Re: [PATCH v3 6/6] ubsan: Include bug type in report header

Andrey Konovalov
2020-01-16T12:32:46Z

On Thu, Jan 16, 2020 at 2:24 AM Kees Cook <keescook@chromium.org> wrote:
>
> When syzbot tries to figure out how to deduplicate bug reports, it
> prefers seeing a hint about a specific bug type (we can do better than
> just "UBSAN"). This lifts the handler reason into the UBSAN report line
> that includes the file path that tripped a check. Unfortunately, UBSAN
> does not provide function names.
>
> Suggested-by: Dmitry Vyukov <dvyukov@google.com>
> Link: https://lore.kernel.org/lkml/CACT4Y+bsLJ-wFx_TaXqax3JByUOWB3uk787LsyMVcfW6JzzGvg@mail.gmail.com
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> lib/ubsan.c | 36 +++++++++++++++---------------------
> 1 file changed, 15 insertions(+), 21 deletions(-)
>
> diff --git a/lib/ubsan.c b/lib/ubsan.c
> index 429663eef6a7..057d5375bfc6 100644
> --- a/lib/ubsan.c
> +++ b/lib/ubsan.c
> @@ -45,13 +45,6 @@ static bool was_reported(struct source_location *location)
> return test_and_set_bit(REPORTED_BIT, &location->reported);
> }
>
> -static void print_source_location(const char *prefix,
> - struct source_location *loc)
> -{
> - pr_err("%s %s:%d:%d\n", prefix, loc->file_name,
> - loc->line & LINE_MASK, loc->column & COLUMN_MASK);
> -}
> -
> static bool suppress_report(struct source_location *loc)
> {
> return current->in_ubsan || was_reported(loc);
> @@ -140,13 +133,14 @@ static void val_to_string(char *str, size_t size, struct type_descriptor *type,
> }
> }
>
> -static void ubsan_prologue(struct source_location *location)
> +static void ubsan_prologue(struct source_location *loc, const char *reason)
> {
> current->in_ubsan++;
>
> pr_err("========================================"
> "========================================\n");
> - print_source_location("UBSAN: Undefined behaviour in", location);
> + pr_err("UBSAN: %s in %s:%d:%d\n", reason, loc->file_name,
> + loc->line & LINE_MASK, loc->column & COLUMN_MASK);
> }
>
> static void ubsan_epilogue(void)
> @@ -180,12 +174,12 @@ static void handle_overflow(struct overflow_data *data, void *lhs,
> if (suppress_report(&data->location))
> return;
>
> - ubsan_prologue(&data->location);
> + ubsan_prologue(&data->location, type_is_signed(type) ?
> + "signed integer overflow" :
> + "unsigned integer overflow");
>
> val_to_string(lhs_val_str, sizeof(lhs_val_str), type, lhs);
> val_to_string(rhs_val_str, sizeof(rhs_val_str), type, rhs);
> - pr_err("%s integer overflow:\n",
> - type_is_signed(type) ? "signed" : "unsigned");
> pr_err("%s %c %s cannot be represented in type %s\n",
> lhs_val_str,
> op,
> @@ -225,7 +219,7 @@ void __ubsan_handle_negate_overflow(struct overflow_data *data,
> if (suppress_report(&data->location))
> return;
>
> - ubsan_prologue(&data->location);
> + ubsan_prologue(&data->location, "negation overflow");
>
> val_to_string(old_val_str, sizeof(old_val_str), data->type, old_val);
>
> @@ -245,7 +239,7 @@ void __ubsan_handle_divrem_overflow(struct overflow_data *data,
> if (suppress_report(&data->location))
> return;
>
> - ubsan_prologue(&data->location);
> + ubsan_prologue(&data->location, "division overflow");
>
> val_to_string(rhs_val_str, sizeof(rhs_val_str), data->type, rhs);
>
> @@ -264,7 +258,7 @@ static void handle_null_ptr_deref(struct type_mismatch_data_common *data)
> if (suppress_report(data->location))
> return;
>
> - ubsan_prologue(data->location);
> + ubsan_prologue(data->location, "NULL pointer dereference");

Not crucially important, but I think it makes sense to use the
single-word-with-hyphens bug type format like in KASAN here, e.g.
null-ptr-deref, misaligned-access, etc.

>
> pr_err("%s null pointer of type %s\n",
> type_check_kinds[data->type_check_kind],
> @@ -279,7 +273,7 @@ static void handle_misaligned_access(struct type_mismatch_data_common *data,
> if (suppress_report(data->location))
> return;
>
> - ubsan_prologue(data->location);
> + ubsan_prologue(data->location, "misaligned access");
>
> pr_err("%s misaligned address %p for type %s\n",
> type_check_kinds[data->type_check_kind],
> @@ -295,7 +289,7 @@ static void handle_object_size_mismatch(struct type_mismatch_data_common *data,
> if (suppress_report(data->location))
> return;
>
> - ubsan_prologue(data->location);
> + ubsan_prologue(data->location, "object size mismatch");
> pr_err("%s address %p with insufficient space\n",
> type_check_kinds[data->type_check_kind],
> (void *) ptr);
> @@ -354,7 +348,7 @@ void __ubsan_handle_out_of_bounds(struct out_of_bounds_data *data, void *index)
> if (suppress_report(&data->location))
> return;
>
> - ubsan_prologue(&data->location);
> + ubsan_prologue(&data->location, "array index out of bounds");
>
> val_to_string(index_str, sizeof(index_str), data->index_type, index);
> pr_err("index %s is out of range for type %s\n", index_str,
> @@ -375,7 +369,7 @@ void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data,
> if (suppress_report(&data->location))
> goto out;
>
> - ubsan_prologue(&data->location);
> + ubsan_prologue(&data->location, "shift out of bounds");
>
> val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs);
> val_to_string(lhs_str, sizeof(lhs_str), lhs_type, lhs);
> @@ -407,7 +401,7 @@ EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
>
> void __ubsan_handle_builtin_unreachable(struct unreachable_data *data)
> {
> - ubsan_prologue(&data->location);
> + ubsan_prologue(&data->location, "unreachable");
> pr_err("calling __builtin_unreachable()\n");
> ubsan_epilogue();
> panic("can't return from __builtin_unreachable()");
> @@ -422,7 +416,7 @@ void __ubsan_handle_load_invalid_value(struct invalid_value_data *data,
> if (suppress_report(&data->location))
> return;
>
> - ubsan_prologue(&data->location);
> + ubsan_prologue(&data->location, "invalid load");
>
> val_to_string(val_str, sizeof(val_str), data->type, val);
>
> --
> 2.20.1
>
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